What Causes Sudden Aggression in Cats?

What Causes Sudden Aggression in Cats?

Animals don't do things without a reason, and cats are no exception. If your feline friend suddenly turns into a hissing, scratching, growling spitfire, there is a reason for this change in behavior. Aggression is defined as the intention to intimidate or dominate, and is a common feline behavioral issue. Unfortunately, an aggressive cat is at risk for being surrendered to a shelter or abandoned outside by a frustrated owner. It can certainly be confusing when a cat suddenly turns her rage on the people who love her. However, there's always a reason and the challenge is to figure out what's upsetting the cat. Read on to learn why a normally docile cat might suddenly become aggressive, and what you can do to help an angry kitty.


While cats are generally solitary critters, they are still sociable and capable of forming close bonds with the people they love. Nonetheless, a cat may become aggressive if she feels threatened, instinctively lashing out to protect herself. For rescued cats, what triggers an aggressive reaction could be related to a bad experience as a stray on the street, or adjusting to life in a shelter. You may not fully understand what's causing the fear or stress. Your cat could also be reacting to other pets in the home or even an atmosphere where people don't get along and are fighting. Some of the most common causes of fear or stress in the life of a cat include new pets in the home, too many pets in the home, sudden movements, sneaking up on them, loud noises, harsh treatment or unfair punishment, being put in a cat carrier, riding in a vehicle, lack of resources (food, water, toys, scratching post), a change in routine or no routine at all.


Anytime a friendly, gentle kitty displays aggression, it's time for a visit with the vet. Cats are stoic and try to hide pain or sickness. A feline could be showing aggression to protect an injury or keep a tender area from being touched. Common causes of pain include dental disease, abdominal pain, arthritis, soft tissue injuries or infections. Sudden aggression can also be caused by neurological issues, cognitive decline, and loss of smell, hearing or sight.

Petting-Induced Aggression

This is a confusing type of aggression that happens when you are calmly stroking your cat and she suddenly turns on you, grabbing your hand with her front claws while trying to shred your skin with her back claws and teeth. It can occur if your cat becomes overstimulated and the pleasant sensation of being petted turns to irritation. It might seem like it came out of the blue for no reason, but your cat was actually giving you signs that she wanted the petting session to end, such as flattened or turned back ears, dilated pupils, stiffening of the body, growling and tail thumping. When you don't notice the signals and carry on with the petting, lashing out is the cat's last resort to get you to stop.

Territorial Issues

Cats aren't afraid to use aggression to protect their territory. Looking out the window and seeing another cat walking around outside could trigger aggression. Other potential triggers are the addition of a new cat or dog in the home, an unfamiliar person in the home, or a move. Sometimes a cat becomes territorial when you give attention to another household pet, and will suddenly attack you or the other pet.

Frustration/Redirected Aggression

Redirected aggression is one of the more common, unpredictable causes of sudden hostility in cats. This is when a kitty becomes hyper-excited, irritated or stressed out by a stimulus that is outside of their reach. For example, when an indoor kitty can't get to that other cat, bird or squirrel on the other side of the window, she has no outlet for her pent up energy and turns her anger on another pet inside the home or on an unsuspecting owner. It's also possible she heard a noise or caught a scent that caused her to be on edge. Many multi-cat families report that when one feline goes to the vet while the other stays at home, redirected aggression can occur against the cat who comes back smelling like that "evil place." These are just a few of the reasons why a happy-go-lucky kitty can suddenly become aggressive. The first thing you should do is schedule a check up with your vet to make sure there isn't a medical reason for the aggressive behavior. If none is found, the next step is to talk to an animal behaviorist who can help you get to the bottom of your kitty's aggression.